Mountain High O2D2 PIREPs with the Scott/Avox O2 system?

[dkkim73]

Hi All, 

To make a long story short, I just bought a Mountain High O2D2 system to make better use of oxygen in my planned flying. 

Read a lot here, including an experience where Don had issues in his Bravo. Spoke to MH support and they thought the system should work in the Acclaim with the Scott/Avox system, using there in-line reducing regulator. There is some conflicting info out there about problems with "altitude compensating regulators" but I am not finding any real technical details to verify pressures, etc. 

Any experience here with this combination? I can probably ops check basic function on the ground or down low, but curious if I will have to fly some higher profiles to verify basic suitability. 

Thanks,

David

 

[Marc_B]

@dkkim73 FWIW, I have a 97 Encore M20K that has a pressure regulator/shutoff valve that "automatically reduces cylinder pressure to the delivery pressure required for operating altitude."  I'm not entirely sure if that's altitude compensation or not, although I always heard that it was.  However in theory, if a regulator was altitude compensating then it should deliver MORE pressure at a higher altitude and less pressure at a lower altitude.

That being said, I have the O2D2 and notice that if I set it on D10 my oxygen saturation measured with a finger pulse ox is good (my "target" is >94%) for up to around 16K.  It seems like a few times around 17/18K I've been 92% with boom cannula and so I've put it on the F1 (lowest face mask setting) and that increases the pulse/duration and bumps me around 96-98%.  Using a Mountain High face mask even on F1 (w/ medium mask) I'm 98% at FL250.  Below 16K I've never had an issue.

As a side note, I've found that MH cannulas DO result in difference in oxygen saturations (boom < traditional).  Supposedly the flared cannula is used if you can't get the unit to sense your inhale, not necessarily for better seal/flow so I've not tried that one.  The boom cannula is the easiest to use, but the most finicky to keep perfectly positioned, which results in sometimes needing an increased flow; but I'd rather use the boom and bump to F1 when I get higher than all the other tubing. (that's just me)

When I'm flying with someone I always monitor it a little more frequently as I'm likely chatting more and the cannulas don't work as well with breathing through your mouth!  I keep one boom and one regular cannula in a bag/seat pocket behind my seat so I have both if needed (which gives me easy access for regular cannula for pax if needed).

As there are so many individual confounders (health, respiratory drive, caffeine intake, hydration level, etc.) that affect oxygen saturation, I'd say the best bet is go on trial runs with at least 1 or 2 pulse oximeters and see where you fall.

EDIT: if you use the O2D2, you have to use their inline reducer or you'll damage the unit if your pressure is too high (see below)

[Marc_B]

Does anyone know what PSI comes out at the Scott connector?  I don't think I've ever seen a chart or documentation for this...but here is what Mountain High says you need as min and max...

[dkkim73]

I had wondered about the output pressures, too, and would think they increase with altitude. 
Looking in the maintenance manual I found a reference to Scott/Avox CRA 895, and found a description online: 

https://www.yumpu.com/en/document/read/32372252/895-series-cylinder-avox-systems-inc

Please note this document covers a range of configurations, so please double-check things if you are relying on it... But it seems to imply the pressures should all be above the range of the inline reducing regulator made by Mountain High (their minimum is 15 psi during inhalation/flow). So I would think if it works down low it should be reasonable to expect it to function correctly higher. Of couse, any assumption needs to be ops-checked for obvious reasons.